Russian Journal of Physical Chemistry A最新文献

An overview is presented of recent advances in applying variational, projection, and diffusion Monte Carlo methods (VMC, PMC, and DMC, respectively). The prospects for using the Monte Carlo method to calculate path integrals (PIMC) when modeling molecular systems are also considered. It is emphasized that modern machine learning effectively meets the requirements of parameterizing wave functions of the target space of solutions for a wide range of problems in quantum molecular modeling and functionals of the corresponding observables.

Abstract—The absorption and luminescence properties of carbon dots based on methacrylate and ethylenediaminetetraacetic acid are considered. The existence of several types of electromagnetic interaction sites is shown. The variation of luminescence spectra with the excitation wavelength is explained. The dependences of the luminescence on the pH, the ionic strength, and the chemical nature of the substance responsible for the required environmental conditions are considered. Strong changes in the carbon dot surface in highly acidic solutions are revealed. The effect of silver nanoparticles on the luminescence properties of carbon dots is discussed. The temporal stability of aqueous solutions of carbon dots is described.

The viscosity properties of binary systems containing the basic amino acid L-arginine (Arg) and nicotinic acid (NA) in water and buffer solution at different concentrations in the temperature range of 288.15–313.15 K were compared. The viscosity of Arg and NA solutions in a phosphate buffer (pH 7.4) was measured for the first time. The concentration dependences of viscosity of the systems obey the Jones–Dole equation for dilute solutions; the obtained values of the B_η coefficient tend to decrease with increasing temperature and reflect the cosmotropic effect of Arg and NA on the solvent. The temperature dependences of viscosity at a fixed solution composition were described using the Arrhenius equation. It was shown that the activation energies of the viscous flow ((E_{eta }^{ ne })) of the systems under study depend linearly on the solute concentration. This made it possible to determine the solvent and solute contributions to (E_{eta }^{ ne }). The Arg and NA solutions in water have lower activation energies than in the buffer. In the given range of concentrations, the (E_{eta }^{ ne }) parameter was found to be mainly determined by the structural contribution of the solvent in which the solvated solute species move.

The authors study the behavior of a mixture of NH₄VO₃, NH₄H₂PO₄, and NaF in a hexane medium during short-term mechanical activation (10 min) in a Pulverisette 7 planetary mill. It is shown that mechanochemical reactions proceed intensely under these conditions to produce a highly aggregated powder containing a mixture of different sodium vanadates and ammonium phosphate vanadates. Monophasic Na₃V₂(PO₄)₂F₃ forms when the powder is subjected to heat treatment. Introducing the disaggregating additive SPAN-80 prevent intensive mechanochemical reactions, thereby leading to a reduction of the content of the Na₃V₂(PO₄)₂F₃ phase in the product to 75 wt %. A content of the target phase as high as 92 wt % was achieved by introducing paraffin into the reagent mixture along with SPAN-80 and subsequent heat treatment in a two-stage scheme that includes compacting the intermediate product. The optimum contents of the additive are selected, and the morphology of the products synthesized using one- and two-stage schemes are studied along with the electrochemical properties of the resulting cathode material.

We present the current state of quantum mechanics, the prospects for its development, and the strengthening of its influence on scientific and technological progress. We look at quantum mechanics from four perspectives. The first perspective astonished physicists already with the advent of quantum mechanics—it is (1) a new way of looking at the world. Over the course of a hundred years of development, quantum mechanics has acquired three more perspectives: (2) an independent field of knowledge, (3) a new physical theory, and (4) a radical change in paradigm in the history of human thought. We have named the new paradigm “neo-Copenhagen” to emphasize both its development from and its continuity with the Copenhagen interpretation. We review the problems of quantum mechanics: how experimental research progresses, how basic concepts develop, how practical applications of paradoxical ideas expand. We indicate ways to solve three Ginzburg’s “great” problems. We formulate the features of the neo-Copenhagen paradigm that have already emerged. We present a look at the future of science and technology on the three time scales.

Magnesium-aluminum hydrotalcite was prepared by the hydrothermal method. By taking advantage of the “memory effect” of hydrotalcite, the calcined hydrotalcite was rehydrated, and simultaneously, ruthenium was impregnated, reduced, and supported to obtain the catalyst Ru/MgAl-RLDH. The specific surface area of the original hydrotalcite MgAl-LDH was 5.1 m²/g, while that of the reconstructed Ru₄/MgAl-RLDH increased to 55.3 m²/g. The total basicity of the surface of the original hydrotalcite MgAl-LDH catalyst was 0.31 mmol/g, and all of them were weak basic sites. The total basicity of the surface of the reconstructed hydrotalcite Ru₄/MgAl-RLDH catalyst was 0.45 mmol/g, and it had more abundant basic sites, including weak basic sites and moderately strong basic sites. The basic sites of the reconstructed hydrotalcite could be systematically adjusted by changing the calcination temperature during the reconstruction process. When the calcination temperature was 400°C and the ruthenium loading was 4 wt %, the Ru₄/MgAl-RLDH catalyst prepared showed the highest activity. Under the optimal reaction conditions (110°C, 11 h, 1 MPa O₂, and a catalyst dosage of 0.08 g), the conversion rate of HMF reached 100%, and the yield of FDCA was 80.9%. Thermogravimetric analysis confirmed that the reconstructed hydrotalcite Ru₄/MgAl-RLDH had better thermal stability than the original Ru₄/MgAl-LDH.

Metal-organic frameworks (MOFs) are widely used as electrode materials due to their porous structure. However, their low conductivity often limits their further development. To overcome the issue, NiCo bimetallic organic framework (NiCo-MOF) and Multiwall carbon nanotube (MWCNT) were attached to Nickel foam (NF) surface without any binder by a simple one-step hydrothermal synthesis, resulting in electrodes with a regular linear layered structure. The structure promoted the electron/ion conduction and exposed more redox active sites, significantly improving electrochemical performance. The electrode prepared with Ni : Co = 1 : 2 and 2% MWCNT exhibited an areal specific capacitance of 5.94 C at 5 mA cm^–2 and the capacity retention rate of 83.1% after 5000 cycles at 15 mA cm^–2. The areal-specific capacitance of the modified electrode material increased by nearly 7 times from 0.87 C to 5.94 C cm^–2. Hybrid supercapacitors (HSCs) consisting of the obtained electrodes and activated carbon (AC) had energy density up to 770 mW h cm^–2 at a power density of 5.63 W cm^–2.

Traditional chemical equilibrium theory posits that reversible reactions can achieve bidirectional dynamic equilibrium under identical thermodynamic conditions. However, this assumption fundamentally contradicts the unidirectionality constraint of the second law of thermodynamics (Δ_rG). Through theoretical analysis and systematic experiments, this study reveals the inherent logical paradox in the traditional definition of reversible reactions: if both forward and reverse reactions must satisfy the spontaneous condition of Δ_rG < 0, they directly violate the second law of thermodynamics. Based on thermodynamic calculations for typical cases such as water electrolysis and calcium carbonate decomposition, as well as unidirectionality evidence from experiments like ethyl acetate saponification and sucrose hydrolysis, this paper confirms that chemical reactions proceed unidirectionally only under specific thermodynamic conditions. The reaction endpoint is determined by reactant depletion or kinetic stagnation, rather than dynamic equilibrium. Isotope tracing technology further validates the unidirectional characteristics at the microscopic level. Accordingly, this study proposes a revised model: the essence of reversible reactions lies in switching reaction directions by altering thermodynamic conditions (e.g., temperature, pressure, concentration), rather than achieving bidirectional dynamic equilibrium under the same conditions. The findings challenge the core assumptions of traditional chemical equilibrium theory and offer a new perspective for the theoretical integration of thermodynamics and reaction kinetics.

Predicting retention indices is of great importance when improving the reliability of chromatography-mass spectrometry analysis. The main means of predicting was once linear equations, constructed for narrow classes of chemical compounds using molecular descriptors. Universal models based on neural networks trained with large databases, have in recent years acquired great importance. The problem of predicting retention indices by means of quantum chemistry has also been discussed in the literature. The aim of this work was to compare all these approaches using 45 aromatic compounds (mostly nitrogen-containing heterocycles) as an example. It is shown that the AIRI neural network is the most accurate and versatile model. Narrowly focused models based on linear regression and molecular descriptors can achieve almost the same (or even better accuracy) for a narrow class of compounds. The least resource-intensive means of quantum chemistry and molecular dynamics cannot reliably estimate the energy of intermolecular interactions, so predicting retention indices ab initio remains difficult for the foreseeable future.

An Al/Fe-silicate composite material is obtained by intercalating Al/Fe polyoxo complexes into the structure of montmorillonite clay with subsequent heating at 350°С. The composite material is studied via energy dispersive analysis, X-ray diffraction, SEM, and low-temperature nitrogen adsorption. It is shown that modifying raises the content of Al and Fe, the pore volume, and the specific surface area, relative to the original clay. The kinetics and equilibrium of adsorption of azo dye Eriochrome Blue SE on an Al/Fe composite material is studied for the first time. The adsorption capacity of the composite material with respect to the dye exceeds that of the clay by as much as 500%. It is established that the main physicochemical parameters influencing the adsorption of the dye are the pH of the dye solution, the content of the sorbent, and the initial concentration of the dye. It is found that the adsorption capacity of the material grows from 5.2 to 26.1 mg/g upon raising the initial concentration of the dye from 15 to 200 mg/L. The efficiency of removing the dye grows along with the content of the material and is 85% at 20 g/L. Raising the pH from 4.0 to 6.5 reduces adsorption through a change in the effective charge of the material’s surface. Results from an analysis using different models of adsorption show that the isotherm of the dye’s adsorption on the composite material is consistent with the Langmuir model (R² = 0.991, Q_max = 36.1 mg/g). A comparison of kinetic data on adsorption and models of pseudo-first order, pseudo-second order, and intraparticle diffusion shows that the kinetics of adsorption is satisfactorily described by pseudo-second order kinetics.